The primary aims of Core C are to: 1) facilitate the design of aging-related surveys around the world and promote harmonization of measures across these surveys; and 2) facilitate national and international comparative analysis based on existing data. The aims will be achieved in collaboration with survey methodologists and researchers in the United States, Canada, Europe, Asia, Latin America, and Africa. We propose five networks, three continuing and two new: Continuing: Disability Trends Network (Robert Schoeni) International Network of HRS Sister Studies (David Weir, Robert Willis) Network on AIDS and Older Persons in Africa and Asia (John Knodel, David Lam) New: Psychology and Aging Network (Jacqui Smith) Network on Effects of Early Life Conditions on Aging (George Alter, Myron Gutmann) Each network is unique in style, membership, geographic range, data sources, and opportunities to advance the field. Their common goals are to exchange material and ideas, improve strategies for data collection, promote comparative research, and disseminate results to a wide and influential audience. The current networks have achieved a high level of informal communication among members. Formal mechanisms include workshops, web sites, and publications. In supporting networks, Michigan continues a long-standing tradition of outreach to developing countries in Asia and Africa, as well as more recent collaborations with developed countries. The HRS Network involves countries in Europe, Asia and elsewhere, helping them design and field longitudinal studies comparable to HRS. The AIDS Network builds on longstanding collaborations In Thailand and South Africa, with extensions to other African countries. The TRENDS network is primarily domestic, but is expanding internationally; members perform policy-relevant analyses of data on disability among the old and near-old.